Layers upon layers, plots within plots. Thursday at Glastonbury used to be simply pitch up, neck 12 hallucinogenic Scrumpys, a quick squelch around Shangri La and then smoke yourself wizard in the Stone Circle. In 2013, though, it's become a frantic hunt for secret thrills. Those vaguely in the know – or alerted by the massive Beady Eye backdrop on the Other Stage – get an early night in preparation for the 11am Friday rush to the weekend's first major "secret" gig in the hope they don't just play Beady Eye songs. Those really in the know descend on the 2000-capacity William's Green tent at 10pm amid whispers of an appearance by Alt-J. Those REALLY in the know blag invite-only tickets to the hospitality stage for an anannounced Stornoway acoustic set. And those not in the know at all just pick a random stage and hope, beyond hope, that Daft Punk will be playing in their tent.

Six By Seven's surprise sets in the Glade – now renamed the Spirit Of '71 stage – have always been a brain-bending joy, and tonight at 9pm the reformed motorik pop noiseniks blast through their entire new album Love And Peace And Sympathy with nary a thought for the "fan favourite" and still inspire people to smear mud on their faces in tribalist mania and do a dance that can only be called Extreme Pinching.

Then, for the ardent scavenger of the secret set, it's a race past the gigantic flame-spewing spider spinning webs of acrobats in Arcadia (one too many Scrumpys?) to the Hospitality stage for 20 minutes being charmed out of your Hunters by a stripped-down Stornoway. Mingling mariachi horns with slapped crate drums they breeze through a heady Zorbing, lost sci-fi party tune When You Touch Down From Outer Space and anti-new build shanty We Are The Battery Human. Mildly drizzly, but quite wonderful.

A dash over to William's Green proves that word is out about Alt-J. The crowd spills a hundred feet out of the tent, grooving glacially to the geometric warps of Tessellate, the spidery subtleties of Matilda and Breezeblocks' blip-funk poundings. They declare themselves Glastonbury virgins but seductively pop Thursday's cherry.

Then it's a squelch through Shangri La where sinners queue to blag their way into the enormous Heaven club, comprising a celestial strip bar and a palatial lounge. Applicants are offered two ways in – convince the angels in the entrance booths of your spiritual purity with a story of your fundamental Mandela-ness or offer them something from your person in return for a wristband. Except, as a lesson in the impossibility of rich men gaining entrance, those wristbands are fake.

Finally, to the Rabbit Hole, which buzzes with word of the ultimate secret set. Michael Eavis, joining the in-house karaoke band for a rousing romp through Suspicious Minds. Which has got to be better than the final secret set we're subjected to, at 6am in the Park camping field, when what sounds like an Ian Brown acoustic session in the tent next to ours starts up to a largely unconscious audience, which swiftly turns nasty. If only we'd camped over in Michael Meads field, at least we'd have got an impromptu acoustic set from Dog Is Dead instead…